Evaluation of Odor and Physicochemical Properties in Sheep Placenta Processed With Different Drying Methods

Sheep placenta is a functional food with proven pharmacological benefits, but its quality is often compromised by conventional drying methods. This study aimed to identify the optimal drying method for preserving the quality of sheep placenta by evaluating the effects of hot air drying (HAD), baking (BK), and vacuum freeze drying (VFD) on its appearance, physicochemical properties, and odor. Physicochemical properties were assessed using colorimetry, texture profile analysis, low-field nuclear magnetic resonance, and amino acid profiling. Volatile compound analysis was performed by headspace gas chromatography-mass spectrometry coupled with an ultrafast gas chromatography electronic nose. Results showed that vacuum freeze dried samples maintained higher lightness, more intact microstructure, better retention of essential amino acids, and significantly lower fishy odor compared to samples treated with hot air drying or baking. Multimethod analysis (Mantel test, Pearson correlation, and TOPSIS) consistently identified vacuum freeze drying as the most effective process. These findings demonstrate that vacuum freeze drying is scientifically preferable for minimizing quality degradation in sheep placenta, providing valuable insights for its application in functional food processing.